The influence of a 3-month antihypertensive treatment on cardiac structure and renal function was assessed in patients with uncomplicated essential hypertension randomly allocated to treatment by the nonselective beta-blocker tertatolol or the angiotensin-converting enzyme inhibitor enalapril. Both tertatolol and enalapril treatments were associated with a similar decrease in mean arterial pressure (-26 ± 6 and -15 ± 2 mm Hg, respectively, both p < 0.05 in comparison with baseline values) and left ventricular mass (echocardiography:-48 ± 17 vs. -18 ± 6 g) but no change in glomerular filtration rate (DTPA clearance). Renal vascular resistance decreased similarly in both groups. Urinary albumin excretion was not significantly modified in either group. These results indicate that a consistent reduction in arterial pressure by either treatment was associated with a proportional change in left ventricular geometry and no alteration in renal function.